Damaged stub up

We have a situation where the toilet stub up has been damaged. There is a crack extending about 1 1/2 " below the top of the floor. This is a basement location so the stubup is in the slab. The floor is ceramic tile which was also installed to "allow" the closet flange to set directly on the slab.

Is it possible to utilize the Fluidmaster extenstion flange to "fix" the crack problem?

I plan to trim the stub up a bit more as it still extends above the floor (tile) level. I also plan to raise the level of the closet flange (not yet installed) by grouting the area where the tile was left out.